And we're back to experimentation, empiricism and prescription. Ever notice that these things always seem to work unless impacted by some outside force (like a closed valve) when applied to the prescription? Goes back to Roland's comment about the numbers being a way to achieve a goal rather than being a physical model of "reality." I recall when the standard changed from using the manufacturer's listed K Factor for standard spray to using the nominal K factor in the standard foe a range. Before there was a Grinnell head that listed about five or so different K factors for one head ranging from 9.0 to 9.7 depending on the static pressure range. The paragraph on the cut sheet following this "precise" parsing then stated to always use 9.2k in all calcs. There was another head (Grinnell or Tyco or both) that may still be out there and maybe not that was QR up to a certain height (say 20') and SR after that. When I see that 2 or 3 heads opening controls 99% of all fires and note that we calc about five times that number it suggests that there is some redundancy built into the model, and after encountering other redundancies throughout the standard, also suggests that following the standard is a safe bet regarding success. Manufacturers (except maybe Chinese copycats) do not put faulty products out or products with parameters too close to the edge, especially when the unpredictability of fluid dynamics in spaces of unknown configuration are involved. (Maybe Turtles feel comfortable playing with that stuff but I sure don't.) Central did not anticipate the O-ring problem and even with all the heads that failed to open I don't recall any (luckily) catastrophic failures involving deaths or major losses. I do recall a restaurant fire where eight Omegas that should have opened didn't and the fire was still extinguished. I'm going to guess that Tyco, RASCO, Viking, Victaulic..., don't market heads they think will, or even might fail. I'll just stick with the prescriptions, content in the knowledge that that CMAs (covers my ...). My bigger issue is with the non-simple strip mall, apartment, office space, etc. system where a tech is left to do the engineers work like defining hazard (and too many under qualified techs go willy nilly into that dark night and then worry about some ten-thousandths place decimal in a prescriptive mathematical model), or just accept water data from some purveyor even when the numbers are physically impossible. My Two Dong (one dong equals 0.00005 dollars, there's a precise number as it has to do with money,and even then that is subject to change as exchange rates fluctuate).
On Fri, May 23, 2014 at 6:02 AM, Richard Mote <[email protected]>wrote: > I can't speak for all of the testing, but I know that when they were doing > full scale testing on the first QR sprinklers, the pressures and flows were > controlled by a computer. During the actual test the computer held the > pressure and flow to 7 psi at 15 gpm and as each sprinkler activated the > computer ramped up the flow and pressure to maintain the minimum operating > conditions at each sprinkler. In most cases 4 - 5 sprinkler controlled the > fire. In one case the computer got behind by about .5 seconds, in that test > over 20 sprinklers were activated and they stopped the test. They reran the > test with sprinklers from the same manufacturer and only 5 sprinklers > activated. This was back in 90, 91 and I'm not sure which testing facility > it was at. > > Richard Mote > Rowe Sprinkler Systems Inc. > > -----Original Message----- > From: Sprinklerforum [mailto: > [email protected]] On Behalf Of Todd - Work > Sent: Thursday, May 22, 2014 5:03 PM > To: [email protected] > Subject: Re: Overpressurizing Heads > > Maybe I am missing something, but when they do a full scale fire test, > doesn't the first head that opens operate in that condition? > > Todd G Williams, PE > Fire Protection Design/Consulting > Stonington, CT > www.fpdc.com > 860-535-2080 (ofc) > _______________________________________________ > Sprinklerforum mailing list > [email protected] > > http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org > -- Ron Greenman Instructor Fire Protection Engineering Technology Bates Technical College 1101 So. Yakima Ave. Tacoma, WA 98405 [email protected] http://www.bates.ctc.edu/fireprotection/ 253.680.7346 253.576.9700 (cell) Member: ASEE, SFPE, ASCET, NFPA, AFSA, NFSA, AFAA, NIBS, WSAFM, WFC, WFSC They are happy men whose natures sort with their vocations. -Francis Bacon, essayist, philosopher, and statesman (1561-1626) A problem well stated is a problem half solved. -Charles F. Kettering, inventor and engineer (1876-1958) _______________________________________________ Sprinklerforum mailing list [email protected] http://lists.firesprinkler.org/listinfo.cgi/sprinklerforum-firesprinkler.org
